| 1 | % \begin{meta-comment} |
| 2 | % |
| 3 | % $Id: exercise.dtx,v 1.2 2003/09/05 16:10:41 mdw Exp $ |
| 4 | % |
| 5 | % Exercises |
| 6 | % |
| 7 | % (c) 2003 Mark Wooding |
| 8 | % |
| 9 | % \end{meta-comment} |
| 10 | % |
| 11 | % \begin{meta-comment} <general public licence> |
| 12 | %% |
| 13 | %% exercise package -- useful macros for setting exercises with answers |
| 14 | %% Copyright (c) 2003 Mark Wooding |
| 15 | %% |
| 16 | %% This program is free software; you can redistribute it and/or modify |
| 17 | %% it under the terms of the GNU General Public License as published by |
| 18 | %% the Free Software Foundation; either version 2 of the License, or |
| 19 | %% (at your option) any later version. |
| 20 | %% |
| 21 | %% This program is distributed in the hope that it will be useful, |
| 22 | %% but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 23 | %% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 24 | %% GNU General Public License for more details. |
| 25 | %% |
| 26 | %% You should have received a copy of the GNU General Public License |
| 27 | %% along with this program; if not, write to the Free Software Foundation, |
| 28 | %% Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 29 | % \end{meta-comment} |
| 30 | % |
| 31 | % \begin{meta-comment} <Package preambles> |
| 32 | %<+package>\NeedsTeXFormat{LaTeX2e} |
| 33 | %<+package>\ProvidesPackage{exercise} |
| 34 | %<+package> [2003/08/25 1.1 Exercies with answers] |
| 35 | % \end{meta-comment} |
| 36 | % |
| 37 | % \CheckSum{271} |
| 38 | %% \CharacterTable |
| 39 | %% {Upper-case \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z |
| 40 | %% Lower-case \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z |
| 41 | %% Digits \0\1\2\3\4\5\6\7\8\9 |
| 42 | %% Exclamation \! Double quote \" Hash (number) \# |
| 43 | %% Dollar \$ Percent \% Ampersand \& |
| 44 | %% Acute accent \' Left paren \( Right paren \) |
| 45 | %% Asterisk \* Plus \+ Comma \, |
| 46 | %% Minus \- Point \. Solidus \/ |
| 47 | %% Colon \: Semicolon \; Less than \< |
| 48 | %% Equals \= Greater than \> Question mark \? |
| 49 | %% Commercial at \@ Left bracket \[ Backslash \\ |
| 50 | %% Right bracket \] Circumflex \^ Underscore \_ |
| 51 | %% Grave accent \` Left brace \{ Vertical bar \| |
| 52 | %% Right brace \} Tilde \~} |
| 53 | %% |
| 54 | % |
| 55 | % \begin{meta-comment} |
| 56 | % |
| 57 | %<*driver> |
| 58 | \input{mdwtools} |
| 59 | \describespackage{exercise} |
| 60 | \let\epsilon\varepsilon |
| 61 | \errorcontextlines\maxdimen |
| 62 | \mdwdoc |
| 63 | %</driver> |
| 64 | % |
| 65 | % \end{meta-comment} |
| 66 | % |
| 67 | %^^A------------------------------------------------------------------------- |
| 68 | % \section{User guide} |
| 69 | % |
| 70 | % The \package{exercise} package allows you to typeset exercises and keep the |
| 71 | % answers together with the questions in your source (so they don't get |
| 72 | % lost) but typeset them all together at the end of your document. |
| 73 | % |
| 74 | % \subsection{Exercises and answers} |
| 75 | % |
| 76 | % \DescribeEnv{exercise} |
| 77 | % Exercises are typset in an \env{exercise} environment. This takes no |
| 78 | % arguments. There's a counter for exercises, named |exercise|, and you can |
| 79 | % cross-reference exercises in the usual way. |
| 80 | % |
| 81 | % \DescribeMacro\answer |
| 82 | % If you want to include an answer for your exercise, just say |\answer| |
| 83 | % followed by your answer. The rest of the text up to the end of the |
| 84 | % \env{exercise} environment is considered to be the answer, and is stored |
| 85 | % away until asked for. This material can contain anything you like. It |
| 86 | % \emph{isn't} a moving argument. |
| 87 | % |
| 88 | % \begin{figure} |
| 89 | %\begin{demo}[w]{The \env{exercise} environment} |
| 90 | %\begin{exercise} |
| 91 | %Show that if $F\colon \{0, 1\}^k \times \{0, 1\}^* \to \{0, 1\}^L$ |
| 92 | %is a $(t, q + 1, \epsilon)$-secure PRF, then $F$~is also a |
| 93 | %$(t, q, \epsilon + 2^{-L})$-secure MAC. |
| 94 | %\answer |
| 95 | %Let~$A$ be an adversary attacking~$F$ as a MAC. Consider the |
| 96 | %adversary~$B$ \ldots |
| 97 | %\end{exercise} |
| 98 | %\end{demo} |
| 99 | % \end{figure} |
| 100 | % |
| 101 | % \DescribeMacro\skipanswer |
| 102 | % The |\skipanswer| command is similar, but just skips over the answer rather |
| 103 | % than writing it to the output file. It does nothing at all with counters |
| 104 | % -- it's as if there was no answer given at all. |
| 105 | % |
| 106 | % It's OK to use commands like |\answer| and |\skipanswer| in your own |
| 107 | % macros as long as they're the \emph{last} token. You can therefore say |
| 108 | % something like |
| 109 | %\begin{verbatim} |
| 110 | %\newcommand{\evenanswer}{% |
| 111 | % \ifthenelse% |
| 112 | % {\isodd{\value{exercise}}}% |
| 113 | % {\answer}% |
| 114 | % {\skipanswer}% |
| 115 | %} |
| 116 | %\end{verbatim} |
| 117 | % to get just the answers to the odd-numbered problems. (If you don't like |
| 118 | % \package{ifthen} then you'll need to play with |\expandafter| for a bit.) |
| 119 | % |
| 120 | % \subsection{The answers file} |
| 121 | % |
| 122 | % \DescribeMacro\answrite |
| 123 | % Answers are accumulated into a file, to be read later. Additional material |
| 124 | % can be added to the file using the |\answrite| macro, which just writes its |
| 125 | % argument. Note that this is a \emph{moving} argument, so fragile commands |
| 126 | % need |\protect|ing. |
| 127 | % |
| 128 | % \DescribeMacro\exctrcheck |
| 129 | % It's common to divide up the answers by section. You can tell the package |
| 130 | % to check a collection of counters and perform actions if they've changed |
| 131 | % since last time, giving you a chance to write the correct decorations to |
| 132 | % the answers file. This is done by saying |
| 133 | % \syntax{"\\exctrcheck{"<counter>"}{"<action>"}"}. Then, each |\answer| |
| 134 | % command checks to see if \<counter> has changed since last time, and if it |
| 135 | % has, it does \<action>, For example, |
| 136 | %\begin{verbatim} |
| 137 | %\exctrcheck{section} |
| 138 | % {\answrite{\protect\subsection*{Section \thesection}}} |
| 139 | %\end{verbatim} |
| 140 | % starts a new (unnumbered) subsection in the answers for each section in the |
| 141 | % main document. |
| 142 | % |
| 143 | % \subsection{Style tweaks} |
| 144 | % |
| 145 | % The \env{exercise} environment is very simple, and can be easily rewritten |
| 146 | % to fit in with your style preferences. If you like exercises to look like |
| 147 | % theorems, the easiest thing to do is say something like |
| 148 | %\begin{verbatim} |
| 149 | %\newtheorem{doexercise}[exercise]{\exercisename} |
| 150 | %\renewenvironment{exercise}{\exfix\doexercise}{\enddoexercise} |
| 151 | %\end{verbatim} |
| 152 | % This makes the environment use the existing exercise counter. If you don't |
| 153 | % want that, say |
| 154 | %\begin{verbatim} |
| 155 | %\newtheorem{doexercise}[othercounter]{\exercisename} |
| 156 | %\renewenvironment{exercise}{\exfix\doexercise}{\enddoexercise} |
| 157 | %\let\theexercise\theothercounter |
| 158 | %\end{verbatim} |
| 159 | % and all will be well. |
| 160 | % |
| 161 | % \DescribeEnv{doanswer} |
| 162 | % Answers are typeset in a \env{doanswer} environment, which is given one |
| 163 | % argument: the exercise number (as set by |\theexercise|). This can be |
| 164 | % modified to do whatever you like. |
| 165 | % |
| 166 | % \DescribeMacro\exfix |
| 167 | % The |\exfix| is a convenient hook which is run both in the \env{exercise} |
| 168 | % and \env{doanswer} environments by default. The current implementation |
| 169 | % just skips a level of \env{enumerate} depth, which usually means that |
| 170 | % \env{enumerate} lists will go (a), (b), (c), \ldots\ rather than 1, 2, 3, |
| 171 | % \ldots |
| 172 | % |
| 173 | % \subsection{Lists in paragraphs} |
| 174 | % |
| 175 | % \DescribeEnv{parenum} |
| 176 | % Answers to subparts tend to be compressed together into a single |
| 177 | % paragraph. It's nice, when you do this, not to have to worry about losing |
| 178 | % your numbering of subparts. The \env{parenum} environment provides an |
| 179 | % enumerated list in a paragraph. So, for example, you can say something |
| 180 | % like this. |
| 181 | %\begin{demo}[w]{Example of \env{parenum}} |
| 182 | %\begin{exercise} |
| 183 | %A PRG $g\colon \{0, 1\}^k \to \{0, 1\}^L$ is \emph{trivial} if |
| 184 | %$k \ge L$. |
| 185 | %\begin{enumerate} |
| 186 | %\item Show that trivial PRGs exist. |
| 187 | %\item Show that a non-trivial $(t, \epsilon)$-secure PRG is a |
| 188 | % $(t, \epsilon + 2^{k-L})$-secure one-way function. |
| 189 | %\end{enumerate} |
| 190 | %\answer |
| 191 | %\begin{parenum} |
| 192 | %\item The identity function is a trivial PRG: the real and random |
| 193 | % games are identically distributed. |
| 194 | %\item Let~$A$ be an adversary attempting to invert~$g$: then we |
| 195 | % can construct a distinguisher~$B$ as follows \ldots |
| 196 | %\end{parenum} |
| 197 | %\end{exercise} |
| 198 | %\end{demo} |
| 199 | % |
| 200 | % \subsection{And finally} |
| 201 | % |
| 202 | % \DescribeMacro\answers |
| 203 | % In order to extract your answers, say |\answers|. |
| 204 | %\begin{demo}[w]{The \texttt{\string\answers} command} |
| 205 | %\section*{Answers} |
| 206 | %\answers |
| 207 | %\end{demo} |
| 208 | % |
| 209 | % The |\answers| command has an optional argument, which is the file to read |
| 210 | % in. This allows you to make `answer booklet' documents, by saying |
| 211 | % something like |
| 212 | %\begin{verbatim} |
| 213 | %\answers[otherdoc] |
| 214 | %\end{verbatim} |
| 215 | % If you don't give a file extension, then |.ans| is appended automatically. |
| 216 | % |
| 217 | % \implementation |
| 218 | % |
| 219 | % |
| 220 | %^^A------------------------------------------------------------------------- |
| 221 | % \section{Implementation} |
| 222 | % |
| 223 | % \begin{macrocode} |
| 224 | %<*package> |
| 225 | % \end{macrocode} |
| 226 | % |
| 227 | % \subsection{Initialization} |
| 228 | % |
| 229 | % The \textsf{within} option is handled by the \package{mdwkey} package. |
| 230 | % |
| 231 | % \begin{macrocode} |
| 232 | \RequirePackage{mdwkey} |
| 233 | % \end{macrocode} |
| 234 | % |
| 235 | % \begin{macro}{\ex@within} |
| 236 | % |
| 237 | % When the \textsf{within} option is seen, we set a command |\ex@within| to |
| 238 | % the correct code, to be executed later when we've made our minds up. |
| 239 | % |
| 240 | % \begin{macrocode} |
| 241 | \let\ex@within\relax |
| 242 | \mkdef{exercise:opts}{within}{% |
| 243 | \def\ex@within{% |
| 244 | \@addtoreset{exercise}{#1}% |
| 245 | \toks@\expandafter{\csname the#1\expandafter\endcsname% |
| 246 | \expandafter.\theexercise}% |
| 247 | \edef\theexercise{\the\toks@}% |
| 248 | }% |
| 249 | } |
| 250 | % \end{macrocode} |
| 251 | % \end{macro} |
| 252 | % |
| 253 | % \begin{macro}{\ex@opts} |
| 254 | % |
| 255 | % The |\ex@opts| macro just runs the \package{mdwkey} kit to parse an option |
| 256 | % string. |
| 257 | % |
| 258 | % \begin{macrocode} |
| 259 | \def\ex@opts{\mkparse{exercise:opts}} |
| 260 | % \end{macrocode} |
| 261 | % \end{macro} |
| 262 | % |
| 263 | % Now do the options thing. |
| 264 | % |
| 265 | % \begin{macrocode} |
| 266 | \DeclareOption*{\expandafter\ex@opts\expandafter{\CurrentOption}} |
| 267 | \ProcessOptions* |
| 268 | % \end{macrocode} |
| 269 | % |
| 270 | % Set up the |exercise| counter, and number it within some other sort of |
| 271 | % counter as appropriate. |
| 272 | % |
| 273 | % \begin{macrocode} |
| 274 | \newcounter{exercise}\ex@within |
| 275 | % \end{macrocode} |
| 276 | % |
| 277 | % We also need the \package{sverb} package in order to do the delaying of the |
| 278 | % answers. |
| 279 | % |
| 280 | % \begin{macrocode} |
| 281 | \RequirePackage{sverb} |
| 282 | % \end{macrocode} |
| 283 | % |
| 284 | % \subsection{Checking for counter changes} |
| 285 | % |
| 286 | % \begin{macro}{\ex@ctrcheck} |
| 287 | % |
| 288 | % The counter checking state is stored here. It's initially empty. |
| 289 | % |
| 290 | % \begin{macrocode} |
| 291 | \def\ex@ctrcheck{} |
| 292 | % \end{macrocode} |
| 293 | % \end{macro} |
| 294 | % |
| 295 | % \begin{macro}{\exctrcheck} |
| 296 | % |
| 297 | % Adding a counter to the check list is relatively easy. We expand the |
| 298 | % current list into a token register, add the new material to the end, and |
| 299 | % put the list back in our macro using |\edef|. The `last' value of the |
| 300 | % counter is set to |\relax|, to force out the change on the next |\answer|. |
| 301 | % |
| 302 | % \begin{macrocode} |
| 303 | \def\exctrcheck#1#2{% |
| 304 | \toks@\expandafter{\ex@ctrcheck\ex@ctrdo{#1}{#2}}% |
| 305 | \edef\ex@ctrcheck{\the\toks@}% |
| 306 | \global\expandafter\let\csname ex@ctrlast@#1\endcsname\relax% |
| 307 | } |
| 308 | % \end{macrocode} |
| 309 | % \end{macro} |
| 310 | % |
| 311 | % \begin{macro}{\ex@ctrdo} |
| 312 | % |
| 313 | % Here we actually check to see whether a counter has changed and execute the |
| 314 | % appropriate code. |
| 315 | % |
| 316 | % \begin{macrocode} |
| 317 | \def\ex@ctrdo#1#2{% |
| 318 | \edef\@tempa{\csname the#1\endcsname}% |
| 319 | \expandafter\ifx\csname ex@ctrlast@#1\endcsname\@tempa\else% |
| 320 | #2% |
| 321 | \global\expandafter\let\csname ex@ctrlast@#1\endcsname\@tempa% |
| 322 | \fi% |
| 323 | } |
| 324 | % \end{macrocode} |
| 325 | % \end{macro} |
| 326 | % |
| 327 | % \subsection{The \env{exercise} environment} |
| 328 | % |
| 329 | % \begin{macro}{\exercisename} |
| 330 | % |
| 331 | % We store the string to print for each exercise in |\exercisename| as a |
| 332 | % half-hearted attempt at internationalization. |
| 333 | % |
| 334 | % \begin{macrocode} |
| 335 | \providecommand\exercisename{Exercise} |
| 336 | % \end{macrocode} |
| 337 | % \end{macro} |
| 338 | % |
| 339 | % \begin{macro}{\exfix} |
| 340 | % |
| 341 | % This is a dumping ground for style fixing common to both exercises and |
| 342 | % answers. Here, we bump on the \env{enum} depth counter, so that it skips |
| 343 | % labelling with digits. |
| 344 | % |
| 345 | % \begin{macrocode} |
| 346 | \def\exfix{\advance\@enumdepth\@ne} |
| 347 | % \end{macrocode} |
| 348 | % \end{macro} |
| 349 | % |
| 350 | % \begin{environment}{exercise} |
| 351 | % |
| 352 | % This is pretty simple. The environment is list-based, with the number set |
| 353 | % in bold in a label. |
| 354 | % |
| 355 | % \begin{macrocode} |
| 356 | \def\exercise{% |
| 357 | \refstepcounter{exercise}% |
| 358 | \exfix% |
| 359 | \trivlist\advance\itemindent\labelsep% |
| 360 | \item[\textbf{\exercisename\ \theexercise}]% |
| 361 | } |
| 362 | \let\endexercise\endtrivlist |
| 363 | % \end{macrocode} |
| 364 | % \end{environment} |
| 365 | % |
| 366 | % \subsection{Answers} |
| 367 | % |
| 368 | % We need a file in which to store our answers. |
| 369 | % |
| 370 | % \begin{macrocode} |
| 371 | \newwrite\ex@ansfile |
| 372 | % \end{macrocode} |
| 373 | % |
| 374 | % \begin{macro}{\ex@ansfilename} |
| 375 | % |
| 376 | % In case anyone has a better idea for a filename than our default, we |
| 377 | % provide a hook. |
| 378 | % |
| 379 | % \begin{macrocode} |
| 380 | \def\ex@ansfilename{\jobname.ans} |
| 381 | % \end{macrocode} |
| 382 | % \end{macro} |
| 383 | % |
| 384 | % We open the file at the end of the preamble, to give the user a chance to |
| 385 | % say |\nofiles|, or change |\ex@ansfilename|. |
| 386 | % |
| 387 | % \begin{macrocode} |
| 388 | \AtBeginDocument{% |
| 389 | \if@filesw% |
| 390 | \immediate\openout\ex@ansfile=\ex@ansfilename\relax% |
| 391 | \answrite\relax% |
| 392 | \fi% |
| 393 | } |
| 394 | % \end{macrocode} |
| 395 | % |
| 396 | % \begin{macro}{\answrite} |
| 397 | % |
| 398 | % This writes stuff to the answers file. We make sure that it's |
| 399 | % appropriately protected, so that you can insert section headings and so on. |
| 400 | % |
| 401 | % \begin{macrocode} |
| 402 | \def\answrite#1{% |
| 403 | \if@filesw% |
| 404 | \begingroup% |
| 405 | \let\protect\@unexpandable@protect% |
| 406 | \immediate\write\ex@ansfile{#1}% |
| 407 | \endgroup% |
| 408 | \fi% |
| 409 | } |
| 410 | % \end{macrocode} |
| 411 | % \end{macro} |
| 412 | % |
| 413 | % \begin{macro}{\answer} |
| 414 | % |
| 415 | % The |\answer| macro needs to read until the end of the enclosing |
| 416 | % \env{exercise} environment (or whatever). |
| 417 | % |
| 418 | % \begin{macrocode} |
| 419 | \def\answer{\sv@readenv\ex@answer} |
| 420 | % \end{macrocode} |
| 421 | % |
| 422 | % Now for the main guts. |
| 423 | % |
| 424 | % \begin{macrocode} |
| 425 | \def\ex@answer#1#2{% |
| 426 | \begingroup% |
| 427 | \@bsphack% |
| 428 | % \end{macrocode} |
| 429 | % |
| 430 | % First of all, check to see whether any counters have changed. |
| 431 | % |
| 432 | % \begin{macrocode} |
| 433 | \ex@ctrcheck% |
| 434 | % \end{macrocode} |
| 435 | % |
| 436 | % Start a \env{doanswer} environment in the file. |
| 437 | % |
| 438 | % \begin{macrocode} |
| 439 | \answrite{\noexpand\begin{doanswer}{\theexercise}}% |
| 440 | % \end{macrocode} |
| 441 | % |
| 442 | % Set catcodes to be strange, and read lines one-at-a-time, writing them to |
| 443 | % the file. When finished, continue at |\ex@endanswer|. |
| 444 | % |
| 445 | % \begin{macrocode} |
| 446 | \let\do\@makeother\dospecials% |
| 447 | \sv@safespc% |
| 448 | \sv@read{#1}\answrite{\ex@endanswer#2}% |
| 449 | } |
| 450 | % \end{macrocode} |
| 451 | % |
| 452 | % When that's done, we wind up here. |
| 453 | % |
| 454 | % \begin{macrocode} |
| 455 | \def\ex@endanswer{% |
| 456 | \@esphack% |
| 457 | \answrite{\noexpand\end{doanswer}}% |
| 458 | \endgroup% |
| 459 | } |
| 460 | % \end{macrocode} |
| 461 | % \end{macro} |
| 462 | % |
| 463 | % \begin{macro}{\skipanswer} |
| 464 | % |
| 465 | % This is much simpler. |
| 466 | % |
| 467 | % \begin{macrocode} |
| 468 | \let\skipanswer\ignore |
| 469 | % \end{macrocode} |
| 470 | % \end{macro} |
| 471 | % |
| 472 | % \begin{macro}{\answers} |
| 473 | % |
| 474 | % The |\answers| macro closes the file, makes sure that future |
| 475 | % \env{exercise}s with answers cause an error, and reads in the file. |
| 476 | % |
| 477 | % \begin{macrocode} |
| 478 | \def\answers{% |
| 479 | \@ifnextchar[{\answers@i\input}{\answers@i\@input[\ex@ansfilename]}% |
| 480 | } |
| 481 | \def\answers@i#1[#2]{% |
| 482 | \immediate\closeout\ex@ansfile% |
| 483 | \global\let\answrite\exerr@toolate% |
| 484 | \ex@withext{#1}{#2}{ans}% |
| 485 | } |
| 486 | \def\q@delim{\q@delim} |
| 487 | \def\ex@withext#1#2#3{% |
| 488 | \edef\next@##1{\noexpand\ex@ext@i{##1}{#2}{#3}#2.\noexpand\q@delim}% |
| 489 | \next@{#1}% |
| 490 | } |
| 491 | \def\ex@ext@i#1#2#3#4.#5\q@delim{% |
| 492 | \ifx\q@delim#5\q@delim\def\next@{#1{#2.#3}}% |
| 493 | \else\def\next@{#1{#2}}\fi% |
| 494 | \next@% |
| 495 | } |
| 496 | % \end{macrocode} |
| 497 | % \end{macro} |
| 498 | % |
| 499 | % \begin{environment}{doanswer} |
| 500 | % |
| 501 | % A very simple environment. We set the exercise number in bold and then |
| 502 | % just write the text. |
| 503 | % |
| 504 | % \begin{macrocode} |
| 505 | \def\doanswer#1{% |
| 506 | \exfix% |
| 507 | \trivlist\advance\itemindent\labelsep% |
| 508 | \item[\textbf{#1}]% |
| 509 | } |
| 510 | \let\enddoanswer\endtrivlist |
| 511 | % \end{macrocode} |
| 512 | % \end{environment} |
| 513 | % |
| 514 | % \subsection{Lists inside paragraphs} |
| 515 | % |
| 516 | % \begin{environment}{parlist} |
| 517 | % |
| 518 | % The \env{parlist} environment is a trimmed-down version of a normal list. |
| 519 | % We todge the |\item| command, make |\list| and |\trivlist| make errors, and |
| 520 | % do various normal list things. |
| 521 | % |
| 522 | % \begin{macrocode} |
| 523 | \def\parlist#1#2{% |
| 524 | \let\@trivlist\exerr@parlist% |
| 525 | \def\@itemlabel{#1}% |
| 526 | \let\makelabel\relax% |
| 527 | \@nmbrlistfalse% |
| 528 | #2% |
| 529 | \let\item\pl@item% |
| 530 | \ignorespaces% |
| 531 | } |
| 532 | % \end{macrocode} |
| 533 | % \end{environment} |
| 534 | % |
| 535 | % \begin{macro}{\pl@item} |
| 536 | % |
| 537 | % This is the implementation of |\item| within a \env{parlist}. The main |
| 538 | % interesting point is the game with boxes, which has the objective of |
| 539 | % extracting the text of the item, together with any style changes set by |
| 540 | % |\makelabel|, but without any stupid bits of glue, or |\llap| or anything |
| 541 | % like that. |
| 542 | % |
| 543 | % \begin{macrocode} |
| 544 | \def\pl@item{\@ifnextchar[\pl@item@i{\pl@item@i[\@itemlabel]}} |
| 545 | \def\pl@item@i[#1]{% |
| 546 | \if@nmbrlist\refstepcounter{\@listctr}\fi% |
| 547 | \setbox\z@\hbox{\makelabel{\global\setbox\@ne\hbox{#1}}}% |
| 548 | \ifvmode\leavevmode\else\unskip\hskip1em\fi\box\@ne~\ignorespaces% |
| 549 | } |
| 550 | % \end{macrocode} |
| 551 | % \end{macro} |
| 552 | % |
| 553 | % \begin{macro}{\useparlist} |
| 554 | % |
| 555 | % We just set the \env{list} environment to use \env{parlist}. |
| 556 | % |
| 557 | % \begin{macrocode} |
| 558 | \def\useparlist{\let\list\parlist\let\endlist\relax} |
| 559 | % \end{macrocode} |
| 560 | % \end{macro} |
| 561 | % |
| 562 | % \begin{environment}{parenum} |
| 563 | % |
| 564 | % Very simple, this. Note that we don't run |\endenumerate|, because that's |
| 565 | % |\let| to |\endlist|. |
| 566 | % |
| 567 | % \begin{macrocode} |
| 568 | \def\parenum{\useparlist\enumerate} |
| 569 | \let\endparenum\endparlist |
| 570 | % \end{macrocode} |
| 571 | % \end{environment} |
| 572 | % |
| 573 | % \subsection{Errors} |
| 574 | % |
| 575 | % \begin{macrocode} |
| 576 | \def\exerr@toolate{% |
| 577 | \PackageError{exercise}{Too late now for \string\answrite}{% |
| 578 | You can't write answers after you've read the file in. I've^^J% |
| 579 | ignored the text you attempted to write. This is why answers^^J% |
| 580 | go at the end of a book!% |
| 581 | }% |
| 582 | } |
| 583 | \def\exerr@parlist{% |
| 584 | \PackageError{exercise}{You can't nest a `list' inside a `parlist'.}{% |
| 585 | I've found a `list' or `trivlist' environment nested inside^^J% |
| 586 | a `parlist'. This isn't allowed. You're probably doomed now.% |
| 587 | }% |
| 588 | } |
| 589 | %</package> |
| 590 | % \end{macrocode} |
| 591 | % |
| 592 | % Done. |
| 593 | % |
| 594 | % \hfill Mark Wooding, \today |
| 595 | % |
| 596 | % \Finale |
| 597 | % |
| 598 | \endinput |